Method of electroplating.



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A GORIPO i'l [DION 015 NEW JERSEY.

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To all whom it may concern:

Be it known, that we, WILLIAM THUM and JoHN J. MULLIGAN citizens of theUnited States, residing at llammond and East Chicago, respectively, inthe county of Lake and State of Indiana, have invented certain new anduseful Improvements in Methods of Electroplatin'g; and we do herebydeclare the following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which itappertains to make and use the same.

The invention relates to electroplating the surfaces of steel, iron,ferrous alloys and kindred base metals belonging to the moreelectro-positive series of metals, with lead, copper or kindred metalsbelonging to the more electro-negative series.

The object/of the invention is to obtain a homogeneous and firmlyadhering deposit of the plating metal directly on the steel, iron orkindred'metal surfaces.

To this end the contact reactions (some of which are of a purelychemical or catalytic action) which usually result from the contact ofthe base metal with the electrolyte containing-acids or producing'freeacids in the process of electrolysis, and which cause such porosity inthe shape of pin holes as to render a thin'plating useless as aprotective covering for the baser metal, are prevented by the directelectroplating of the surfaces of the base metal with an initial thin,smooth, homogeneous and adhesive coating ofa plating metal such as leadwhich protects the base-metal from contactwith the electrolyte duringthe continued deposition of the plating metal.

ile the invention may be employed with advantage in the.electrodeposition of various. metals on iron, steel. and ferrousalloys, it is particularly adapted for the electro-de ositidn of lead,and its application to lead p ating will be specfically described.

The preferred procedure to obtain the desired electro-plated coating isas follows.

The surfaces of the articles to be plated are first cleansed of foreignadherences, such as oxide, grease and slags. This cleansing operationmay beefi'ected in the usual way by acid and alkaline dips orpickles,but we have found that a sand blast applied 1n a i suitable manner isquite satisfactory for this purpose.

Specification of Letters Patent.

Application filed July 31, 19M. fierial No. MLIWTO.

Patented n w. a ft.

The next step in the process istowarm the thus prepared article to adesired temperatu e of to degrees Fahrenheit. This operation ispreferably done immediately after the cleasing operation so as to avoidany possibility of oxidation or condensation of moisture on the surfaceto be plated.

The article may then be connected with the source of the de ositingcurrent, either by a flexible or rigi conductor, and immediately dippedinto a solution of animal gelatin and clean water, which solution ispreviously prepared by dissolving the gelatin in the water at atemperature of about degrees F. The percentage of gelatin in thesolution can be varied to some extent, but is preferably approximatelytwo per cent. When plating the interior of a container or other article,it is found to be more convening'steps in the process.

The next step, which, to secure the best results, should be performedimmediately after the article has. been dipped, or after the solutionhas been emptied from themterior of the article, as the case may be, istotransfer the article to the plating bath or, if the sha e of thearticle permits, it may be filled with the electrolyte. As the articlehas previously been connected with the electric current, electrolyticaction-takes place at the moment of contact of the article andelectrolyte.

Tn the plating operation we have found that the use for a short space oftime of an initial current of abnormally high density results in thedeposit upon the base metal surface of a erfectly homogeneous coveringwhich. will uild further without porosity after thec-urrent density hasbeen lowered to normal. 4

As a normal current density with moderlib till

ate circulation of the electrolyte, we have 1 found that 10 to 15-amperes per square foot give satisfactory results. For the initialexcessive current density, which need only be applied for a few seconds(less than a minute) we have found that 25 to 50 amperes solution isemployed, a lead contents 11 per cent. and a total hydrofluosilicic acidcontents of to 12 per cent. is recommended.

In explanatlon of the assumed reactions taking place during the severalsteps of the I process, it appears evident that the formation of minutegas globules which would otherwise be caused by chemical reaction at themoment of contact of the base metal to be plated and the acidonstituents of the electrolyte is 'prevented by the gelatin solution. Itacts as a momentary protective coating against direct contact of theelec-. trolyte, and simultaneously the overpowering electric energy ofthe excessive current density deposits an initial homogeneous andprotective metal coating in the shortest possible interval and beforethe protective'gelatin, coating has been fully difi'used with theelectrolyte wherein it acts as an addition agent to promote a smoothelectrodeposit.

When lead is used as the anode, it should preferabl be of the highestpurity, and it can be cast into any convenient shape to suit therequirements; moving either one of the electrodes, a'much increasedmixing or circulating of the electrolyte can be brought about, therebypermitting a relative increase inthe excessive and normal currentdensities and consein the rate of deposit. g n practlsing th sinvention, other com pounds containing an addition agent actingsimilarly to animal gelatin can be-used as the initial protective andsoluble coating but this will obviously in no way changethe principlesof the invention.

at is claimed is v 1. The method of electroplating which By rotating orotherwise gelatin, connecting the article to be an Initial current ofabnormally high density, reduced interval.

3. The method of electroplating which consists in covering the surfaceto be plated with a film of gelatin solution and then depositing'theplating metal thereon by electrolysis with an initial current ofabnormally high density reduced to normal after a short interval.

4. The method of directly electroplating the surfaces of iron, steel andkindred base metals which consists in covering thesurface to be platedwith a protective film soluble and difiu'sible in the electrolyte,subjecting the same to the action of a lating bath current having anabnormal y high current density for a short interval, and then reducingthe current density to normal until the desired thickness of deposit hasbeen obtained.

5. The method of directly electroplating the surfaces of iron, steel andkindred base to normal after a short metals which consists in coveringthe surface to be plated with a protective film of latcd to the sourceof electric current, and t en subjecting'the same to the action of aplating bath current having an abnormally high current density for ashort interval, and then reducing the current density to normal untilthe desired thickness of deposit has been obtained.

WILLIAM THU'M. JOHN J. MULLIGAN.

